Amplifier for subscribers&#39; stations



June 9, 1925.

$.STRAUSS AMPLIFIER FOR SUBSCRIBERS STATIONS Filed June 1, 1922 2 Sheets-Sheet 1 W5, W Z mw M &% W

June 9, 1925.

I 1,541,668 S. STRAUSS AMPLIFIER FOR SUBS'CRIBERS STATIONS Filed June 1 {9 22 .2 Sheets-Sheet 2 Patented June 9,1925.

UNITED STATES PATENT OFFICE.

AMPLIFIER FOR SUBSGRIBERS STATIONS.

Application filed me 1, 1922. Serial No. 565,121.

fact that the voice of such person is also The amplifier V, is a thermionic relay, it amplified. comprising an incandescent cathode K In the accompanyingdrawingk 'anode or plate A and a grid H The grid Fig. 1 shows the connections of the amis connected with the secondary S of the 100 plifier when working in a local battery sysfirst repeater N,. The negative side of the tom and employing two vacuum tubes that battery B B is connected with the con- To all whom it may concern:

Be it known that I, SIEGMUND STRAUSS, citizen of the Republic of Austria, residing at Vienna, Austria, have invented certain new and useful Improvements in Amplifiers for SubscribersStations (for which I have filed applications in Austria December 25, 1920; Germany, .April 25, 1922; Czecho- Slovakia, Dec. 23, 1921; Austria, June 1, 1912; Germany, June 11, 1921; Austria, Jan. 12, 1922; Austria, Feb: 11,1922), of which the following is a specification.

This invention relates to am lifiers for telephonic currents and especial y to those which are to beprovided in the subscriber's stations to amplify trunk line or local communications, and it has for its object to provide a simplified and improved arrange ment which enables theisubscriber as well as the operator of a branch or house exchange to connect the amplifier, at will, with an existing SIlbSGIZlbGIYS StatlOII of either the local or the central battery type, according to requirements, the present invention enabling these results to be obtained without requiring special adaptation reconstruction or other alteratioi'i' of the existing type of station.

A further object of this invention is to provide ,an" arrangement'by means of which one or more amplifiers of the vacuum tube type can be insertedby a simple manipulation, whereby it is possible for the operator of a manual'or other house exchange as well as the person speaking from a substation connected to said house exchange to use theamplifier, according to requirements, when receiving telephonic messages. I.

A further object of this invention is to remove all whistling or extraneous noises in the receiver due to the connections, as well as to prevent any disturbing influence due to the voice of the, individual speaking at the exchange or sub-station, due to'the may be connected in series.

scribers stations of the central battery type, having a single amplifier of the vacuum tube type.

Fig. 3 shows the connections for a house exchange of the local battery type, which permits not only the operator, but also the diiterent subscribers stations to receive amplified trunk communications by simply uslng an additional single conductor.

Fig.1 illustrates the application of the present invention to a subscribers station when such-station is of the local battery type, it being well known that in subscribers stations of the local battery type the microphone M, the local battery B and the primary P of the induction coil are in one circuit. The primary P acts on the secondary S which is connected with the trunk lines L and L Accordingto this invention, one of the trunk lines, line L for example, is connected through the switch J wlth the primary EG of the first repeater N The middle of the primary EG of the first repeater N is connected with the secondary S of the induction coil through the switch J,. .The other end of the secondary S is con'nected with the point D of the trunk line L The end G of the primary EG of the first repeater N is also connected with the point D through [the resistance .R and the switch J The resistance R'as so chosen that it equals, so"

? pable of establishing a direct communica- ,tion between the subscribers telephone and the trunk lines independently of the amplifier V so that the speaking current can be received without amplification.

- ductor O at the point F rises the contact springs 4 and 5 of the ey T,,'the primary P of the last repeater N and the battery B The secondary S of the last repeater is in parallel with the receiver T.

The key T allows a second amplifier V to be connected in series with the first am; plifier V For this purpose, it comprises a number of contacts 1, 2,73, 4 and 5 which clcontrol the circuits of the second amplifier. The heating current for the cathode or filament K of the second amplifier is controlled by the contacts 1 and 2 of this key, and'the contacts 3 and 4 of the key control the primary P of an intermediate repeater N the secondary S of this intermediate repeater being connected with the grid H of the amplifier V If the switches I, J, J,, J 2 and J 3 are in the position shown in dotted lines, the amplifier is switched off and the current coming from the trunk line L flows over the switch J, conductor L, switch J receiver. T, conductor 0, to the secondary S of the induction coil thence through connection point D and back to the line L The microphone current flows through the primary P of the induction l coil, the battery B and back to the microphone M. V

When the microphone M is actuated whlle the amplifier is switched ofi the speaking currents,- induced in the secondary S of the induction coil will pass into the trunk lines L and L,, the current flowing to trunk line L directly over the connection point D,

while it flows to trunk line L and also through the conductor 0, receiver T, switch J conductor L, switch J and thence to the trunk line Lg. On the other hand, if the amplifier is working, in which case all switches are thrown into the full line positions shown, the incoming speech currents from the trunk line L, flows over the switch J to connection point E of the first repeater N through the same over connection G, resistance R, switch J connection D back to the trunk line L, and thus acts fully on the first repeater. A feeble shunt to this microphone current exists through the trunk line L,, connection E of the first repeater, connection F, and secondary S of the induction coil to connection D; but as the current in such shunt flows in the same direction as the current flowing through the connection G and resistance R, no interference between the said currents will occur.

The incoming speech currents thereforel fully act on the first repeater N and are amplified by the thermionic relay V in a known manner. The amplified current flows from battery B through the filament K the plate A the springs 4 and 5 of the key T. and through the primary P of the last repeater N back to the batte This current therefore acts on the secon ary S, of the last repeater N the secondary S being in' parallel with the receiver T and switch J At the same time the connection point F is connected with the negative pole of the heating current battery through point F The connection 0, which establishes a permanent connection between the secondary S and the connection poin'oF of the first repeater N causes 'no disturbances of the amplified current; on the contrary it was-observed that whistling or other noises in the receiver is prevented thereby.

In the position of rest of the key T as shown in Fig. 1, the heating current of the.

tery pole of the battery B by the open con tacts 1 and 2 of the key T consequently the second relay is not working. phone current stepped up in the winding S of the first repeater N acts on the incandes-. cent cathode K and the grid H of the first amplifier. Theamplified current flows from the negati e pole of the battery B through the incan escent cathode'K to the anode A thence through contacts 4, 5 of the key T and over the primary P of the last 1'e-' peater N and then back to the positive pole of the battery B supplyin current. At this time the primary P of tfie'intermediate repeater N is switched of]? by the open contact 3 of the key T and thesecond thermionic relay V the cathode" of which ,is not heated forms an infinitelv high resistance between its anode A an its cathode K The amplified current will therefore act directly in the last repeater N and receiver T as set forth above. 'A single stage of amplification of the incoming microphone current is thus obtained; 7

If the second relay is to be connected in series with the first one to obtain ahi her amplification, the key T is operated; hen the key T is actuated the heating circuit-of the incandescent cathode K of the second amplifier is closed with the batter B by the engagement of the contact 1, 2. he current then flows from the negative side of the heating current battery B throu h contacts1,2 of the key T through incandescent cathode K and back to the positive side ofthisbattery. The primary P of the intermediate repeater N is then connected as follows: negative side of battery B cathode K anode A engaged contacts 4, 3 ofthe key T primary P of the second repeater,

and then back to the positive side of the battery B the current flowing through this circuit therefore acting on the second relay V through'the secondary S of the interme- The microdiate repeater N,. The anode circuit of the secondthermionic relay V extends from the negative side of the heating battery B through engaged contacts 1, 2 of the key'T thence through cathode K and to the anode A,. This circuit is interrupted at open contact 5 of the key, and hence this current will flow back to the-positive pole of the anode current battery 2 ondary S of the last repeater 1s shown,

which is connected with the point F of the primary E, G of the first repeater coil. With respect to the amplifier arrangement, Fig. 2 is, therefore, identical with Fig. 1, or may include only one amplifier, omittlng the switch T and the second amplifier controlled thereby.

The modification with respect to Fig. 1 resides mainly in the arrangement of the circuits in the subscribers station hereinafter described.

In this arrangement M desi nates the microphone, and P the primary 0 the induction coil of the subscribers station, which is connected with connection point D of the trunk line L over the closing contact ofthe hook switch H. Other reference letters are identical with those appearing in Fig. 1. The microphone is arranged in series with primary P while its other end is connected to the'trunk line'L, when the amplifier is not inaction, or over the battery B with connection point F of the first repeater E, G when the amplifier is switched in. A choke coil D may be connected in parallel with the microphone as shown.

The circuit containing the receiver T, the,

condenser K, and the secondary coil S is not closed in this case, as usual, but is connected with the connection point 0 between the microphone and the primary coil.

The amplifier is connected with the secondary of the first repeater E, G in the same way as shown in Fig. 1. Y

The switches J J J position they occupy, allow the telephonic message to be received with or without amplification. When the amplifier is out out,

the switches J, J J J are in the position shownin the dotted lines.

The incoming current flows in this case from the trunk line L over switch J and switch J (both in the position shown in J according tothe dotted lines) through the microphone. M,

the primary P, the hookswitch H in its closed position, and over connection point D backv to the conductor L The receiver current is stepped up in the coil S and flows from S over the receiver .T, the condenser K, connection point Q, microphone M and point 0 back to the induction coil S.

When the amplifier is switched in, the

switches J, J,, J J 3 must be brought into the full line positions shown. The incoming current flows from the trunk line L,, through the primary E, G of the first repeater and then through the artificial resistance R and connection point D back to the line I L,,.

There also exists a second path over F, F,, U and the secondary S, but owing to the high alternating current resistance of this coil, this does not impair the operation. In any case, the whole current will flow back to the trunk line L The current passing through repeater E, G is amplified by means of the amplifier not shown connected to the secondary of the repeater E, G, and is then in. its amplified condition, it acting upon the.

coilN of the last repeater. The amplified current passes over switch J 3 to the receiver and returns to coil N over U and F The microphone currents produced in the sub-station flow from battery B and microphone M through the primary P of the subscribers induction coil P and over the hook switchH to point D and trunk line L and, on the other hand, they pass the points U,

F and F and flow over switch J to the second trunk line L,.-

In this case the microphone has its own battery B which may be identical with the battery used for,heating the incandescent cathode of the amplifier tube or tubes because such a battery is used only when the amplifier is used; otherwise the microphone can derive its current from a central battery. This special microphone current is stepped up by the induction coil before passing out to the trunk lines. By inserting the battery amplif ing device if the resistance of the trunk ine is equal or nearly equal to that of the artificial resistance R.

to allow the connection of the amplifier arrangement withany subscribers station regardless of the system, and to amplify the incoming speech currents. The outgoing currents are not I amplified and therefore noises in the receiver are suppressed, un desired feed backs are eliminated and, furthermore, the voice of the person speaking The principal object of the invention is-' at the station does'not sound disagreeably loud in the receiver.

Fig. 3 shows the connections of an amplifying device for a house exchange, ,it per- 6 mittmg not only the operator, but also,'if

required, the sub-station connected with the house exchange, to receive the incomin trunk communications in v amplified condition.

In this figure, a sub-station of the local battery type is shown, but it is obvious that a, sub-station of. the central batter may also be employed without changing the conditions.

. The arrangement oithe connections of a house exchange -is known, and, therefore, is not shown in this figure. Two plugs are provided, onewith two contacts X, Y, and one with three contacts, 7-, s, t. 'The line through contact s-leads to the middle of the those used in Figs. 1 and 2.

X of plug to connection point E of the primary of the first repeater N and from the end thereof at G through the resistance R, point D. and the contact 'Y of the plug back into the trunk L, and this current is therefore amplified in the amplifying device by means of the secondarg connected to the grid of the amplifying evice V,. a The amplified current flows from the sec ondary S of the last repeater, through the additional conductor L and plug contact .9 to point U, thenctQthrou h the receiver T of the sub-station, then-t rough conductor L and lug contact t, and back to the secondary g, of the last repeater N so that the microphone current may be received in am lified condition in the receiver T of eac sub-station connected in this manner.

The outgoing micro hone current produced in the secondar gfiows from connection point U throug the additional conductor L and'contact 8 of the plug, to connection point F of the first repeater N thence to point E, contact X of plug, through trunk line L. back over trunk hne L through contact Y of plug, to connection int D, thence through contact 1' of the ug, and conductor L to the other end of the induction coil S. Over the resistance R a shunt exists, which is of no consequence. In this way, it is possible, with a single am lifier in the house exchange, and a specia conductor for each sub-station, for the operator or any person in one of the sub-stations to receive amplified trunk current.

Of course, as already described, with reftype erence to Figs. 1 and 2, the o erator in the house exchange, as well as t e subscriber,

phone lines, and a subscribers station at the ends of the lineshaving a microphone, a

telephone and an induction coil, an amplifier.

for amplifying, the incoming speech currents, a telephone repeater having a primary and a secondary, a connection including an artificial resistance substantially equal to the line resistance connecting said primary with the telephone lines, means for connecting said microphone to the primary of said repeater whereby the, currents from said microphone remain unaniplified, asecond telephone repeater operatively connected with the amplifier and having a secondary operatively connected with the subscribers telephone and a connection between the secondary of said repeater and the middle of the primaryof the first telephone repeater.

2. In a telephone system comprislng tele-,

phone lines, and a subscribers station at the ends of-the'lines having a microphone, a telephone and an induction coil, an amplifier for amplifying the incoming speech currents, a telephone repeater having a primary and a secondary, a connection including an artificial resistance substantially equal to the line resistance connecting said primary with the telephone lines, a bridge between one of said lines and the middleof the primary of said repeater, said bridge andconnection being operable to cause amplification of the incoming speech currents but tocause the currents from said micro hone to remain unamplified, a second te ephone repeater operatively connected with the amplifier and having a secondary operatively connected with the subsc'ribers telephone, and a connection between the secondary of said. repeater and the middle of the primary of the first telephone repeater.

3. In a telephone system comprising telephone lines, and a subscribers station at the ends of the lines having a micro hone, a telephone and an induction coil, an mplifier for amplifying the incoming speech currents, a telephone repeater having a primary and a secondary, a connection including an artificial resistance substantially equal to the line resistance connecting said primary with the telephone lines, a bridge between one of said lines and the middle of the primary of said repeater, said bridge including a wind telephone, and a-connectionbetween the .sec-

ondary of said repeater and the middle of the primary of the'first telephone repeater.

4;. In a telephone system'comprising tele- I phone lines and a subscribers statio'n'at the ends of the lines having a microphone, a

telephone and an induction coil, an amplifier consisting of a vacuum tube'with a heated cathode, a grid and an anode thereln, a source of current for heating said cathode, a telephone repeater having a primary and a secondary, a connection including an artificial resistance substantially equal to the line resistance connecting said primary w1th the telephone lines, means for connecting said microphone to the primary of said repeater whereby the-.currents from said microphone will remain unamplified, the sec; ondary of said repeater being connected w1th the grid circuit of the amplifier and the heated cathode and with themiddle of the the telephone. lines, a bridge-between one of primary of said repeater. 0 o

5. In a telephone system compr smg tele phone lines and a subscribers station at the ends of the lines having a microphone, a telephone and an induction coll, an amplifier consisting of a vacuum tube with a heated cathodefa grid and an a'node there1n, a source of current for heating said cathode, a telephone repeater having a pr mary and a secondary, aconnection mcludlng an artificial resistance substantlallly equal to the line resistance connecting sai primary with said lines and the middle of the primary of said repeater, said bridge includ ng one winding of the subscribers induct on coil, said bridge and connection 'bemgcperable to cause amplification of the incoming speechcurrents but to cause the currents from said microphone to remain unamplified, a second telephone repeater connected with the subscrlbers te ephone, a connection between the secondary of said repeater and the middle of the prlmary of the first telephone repeater, a controlling circuit cathode and the midd rents, a ephone repeater 'for the am lifier connected with the secondar of t e first repeater, and a connection I etween the su ply circuit of the l e of the primary of the first repeater.

6. In a telephone system comprising telephone lihes and a subscribers station at the ends of the lines-having a microphone, a telephone'ahd an induction coil, an amplifier for ampli ing the. incominfi speech curavmg a priolperatively mary and a secondary, a-connection including an artificial resistance substantially equal to the line resistance connecting said primary to the telephone lines, a brid e be tween one of said lines and the mid e of the primary of said repeater, said bridge including one winding of the subscribers induction coil, the other win being directly connected with the termina of the winding included in said bridge said' connection and bridge being 0 rable to cause amplification of the incoming speech currents but to causethe currents from said microphone to remain unamplified;

7. In a telephone system comprising telephone lines and a subscribers station at the ends of the lines, having a microphone, a telephone and an induction coil, an amplifier for amplifying the incoming speech currents, a telephone repeater having aprimary and a secondary, a connection includin -an artificial resistance substantially equa to the line resistance connecting said primary to the telephone lines, a bridge between one of said lines and the middle of the rimary of saidrepeater, said bridge inclu ing one winding of Athe subscribers induction coil, the other windin of said induction coil being branched o from the terminal of the wlnding included in said bridge, said bridge and connection being operable to cause amplification of the incoming speech currents.

tively connected with the subscribers telephone, and a' connection between the aeconaryof said re eater and the middle of the primary of first telephone repeater.

t 8. In a telephone system comprising telephone lines and a subscribers station at the ends of the lines havi a microphone, a telephone and an inductlon coil, an amplifier for amplifying the incoming h currents including means whereby the currents from said microphone remain unamplified, a secondamplifier capable of further amphfying the output currents of the first amplifier, a telephone repeater having a-primary and a secondary, the primary being connected with the telephone lineand the secondary with the first amplifier, a second telephone re ater having a primary and a secondary, t e primary branching 01! from the output circuit of the second am lifier,

and the secondary being connected with the subscribers telephone, and a multiple switch controlling the working circuit of the second amplifier, comprising means (capable 1 'fier for amplifying the incoming .ends of the lines having microphone, a telephone and an induction coil, an amplicontrolling the energizing circuit of said second amplifier, a third repeater having a primary capable of being connected with the output circuit of the first'repeater by the said multiple switch, and a secondary in operative connection with the second amplifier, said multiple switch including contacts capable of connecting alternately the primary windings of the second or third repeater with the output circuit of said am plifier.

10.'In a telephone system comprising telephone lines and a subscribers station at the ends of the lines having a microphone, a telephone and an induction coil, an amplitelephone currents including means where y the cur- ==rents from said micro hone remain unamplified, a second amp 'fier for increasing the amplification obtained by the first amplifier, a multipleswitch controlling1 simultaneously the output circuitof t e first amplifier and the working circuit of the second'amplifier, said switch being provided with means for connecting alternatel the out ut circuits of the first and secon ampli ers with the subscribers station telephone. i

11. In a telephone system comprising telephone lines and a subscribers station at the ends ofthe lines having a microphone, a telephone and an induction coil, an amplifier for amplifying-the'telephone currents transmitted to the subscribers telephonefa repeater having a primary connected with the tele hone line and a secondary connected Lnected with the primary of wit the input circuit of said amplifier, means for connecting said microphone to the primary of said repeater whereby the currents from said microphone will remain un amplified, a second repeater having .a pri mary connected with the output circuit of said amplifier, and a secondary connected with the subscribers telephone,- a second amplifier having an output circuit etpllally cont e second repeater, an intermediate repeater with a primary capable of bein connected with the output circuit of the rst amplifier and a secondary connected with the input circuit of the second amplifier, and a multiple a telephone and an induction coil, an amplifier for amplifying the incoming telephone currents, a telephone repeater having a 'pri vmary capable of being connected with the line and a secondary connected with the inputcircuit of the amplifier, means for connecting said microphone to the primer of said repeater whereby the currents rom said microphone will remain unamplified, a second repeater having a primary capable of being connected with the output circuit of the repeater and a secondary connected with the'subscribers telephone, a connection between said secondary and the middle of the primary of the first re' ater and a further connection between sai secondary and the telephone line, and switch arms v:Eor alteran artificial resistance substantially equal y to the line resistance, and a secondary connected with the input circuit of the amplifier, a brid between one of said lines and the mi dle'of the primary of the re peater, said connection and brid 'being operable to causeamplification 0 the incoming as hi currents butv to cause the currents rom said microphone to remain unamplified, said bridge inclndin a switch arm capable of disconnecting t e bridge I connection from the said pr mary, 1!. second repeater, havin a primary capable of being connected wit the output circuit of the repeater and a secondary connected with the subscribers telephone, a connection between 'sai secondary and the middle of the primary of thefirst repeater, a further connection between said secondary and the telephone line, and switch arms adapted'tobe operated simultaneously with the switch arm in the brid e for alternatel opening and closing sai connection an the connection between the primer ,of the first repeater and the line as we asythe cannection between the secondary of this second repeater with the subscribefls tele phone.

i 14. In a telephone system comprising telephone trunk lines and a subscribers station at the ends of the lines having a microphone, a telephone and an induction coil, an amplifier for amplifying the incoming telephone currents, a telephone repeater having a primary connected with both trunk lines, said connection including an artificial resistance substantially equal to the line resistance, and a secondary connected with the input circuit of the amplifier, a bridge between one of said trunk lines and the middle of the primary of the repeater, said bridge including the secondary winding of the induction coil of the subscribers station, said connection and bridge being operable to cause amplification of the incoming speech currents but to cause cur rents from said microphone to remain unamplified, the primary winding of said induction coil being connected immediately in series with the secondary, the connection between the middle of the primary of the repeater and the induction coil branching off at an intermediate point between the primary and the secondary of the induc tion coil and including the microphone whereby the energizing current of said microphone is prevented from acting upon the amplifier.

15. In a telephone system comprising telephone trunk lines and a subscribers station at the endsof the lines having a microphone, a telephone and an induction coil, an amplifier for amplifying the incoming telephone currents, a telephone repeater having a primary connected with both trunk lines, said connection including an artificial resistance substantially equal to the line primary of said repeater, a second telephone repeater having a primary connected with the output circuit of the amplifier, and a secondary operatively connected with. the subscribers telephone, switch arms capable of alternately opening and closing this connection and the connection between the trunk line and the primary of the first telephone repeater simultaneously with the switch arm in the bridge, the battery providing a connection of the telephone directly with the trunk lines or over the amplifier, the switch arm in the bridge "-when open disconnecting the microphone and the feeding battery, thereby establishing direct conpection between the telephone and the trunk In testimony whereof I afiix my signature in presence of two witnesses.

ING. SIEGMUND STRAUSS.

lVitnesses:

CARL CONDENBURY, JosEF GURMANN. 

